Encoder

• US 4,465,373 A
• Filed: 06/15/1981
• Issued: 08/14/1984
• Est. Priority Date: 06/17/1980
• Status: Expired due to Term

• Current Assignee: K. K. Topcon
• Original Assignee: Tokyo Kogaku Kikai Kabushiki Kaisha
• Inventors: Ohtomo, Fumio, Tamaki, Hiroshi, Kimura, Kazuaki
• Primary Examiner(s): Rosenberger, R. A.
• Application Number:
  US06/273,772
• Time in Patent Office: 1,156 Days
• Field of Search: 356/373, 356/374, 250/237 G, 33/125 A, 33/125 C, 33/1 M
• US Class Current: 356/617
• CPC Class Codes: H03M 1/203 using an analogue interpolation circuit
• CPC Class Codes: H03M 1/285 of the unit Hamming distance type, e.g. Gray code

Abstract

An interpolation encoder comprising a sensor array, a code plate arranged in opposition to the sensor array and having a plurality of groups of lattice patterns, and an arithmetic unit for processing data of the code plate detected by the sensor array. The lattice patterns of at least one of the groups are inclined.

Claims

1. An interpolation encoder comprising a sensor array having a plurality of sensor elements continuously arranged in an array, a code plate which has periodic lattice patterns including lattice pattern information "1" and "0" alternately and which is arranged in opposition to said sensor array, and an arithmetic unit for processing data detected by said sensor array from said lattice patterns of said code plate, characterized in that;

said lattice patterns are formed by inclined lattice patterns whose arrangement is inclined with respect to the arrangement of said sensor elements of said sensor array for providing detection sensitivity in two-dimensions for said sensor array,

whereby the number of the lattice patterns within a predetermined length of said code plate is slightly different from the number of said sensor elements of said sensor array within a length corresponding to said predetermined length so that a vernier relationship is established between the lattice patterns of said code plate and said sensor array, and

said arithemtic unit is provided with means for obtaining an intersected position of an output envelope of even-numbered elements and an output envelope of odd-numbered elements of said sensor array for obtaining an interpolated value within the width of the sensor element.

2. An interpolation encoder according to claim 1, characterized in that said code plate has a plurality of said groups of lattice patterns, and said lattice patterns of at least one of said groups of lattice patterns comprise said inclined lattice patterns.

3. An interpolation encoder according to claim 2, characterized in that said lattice patterns of at least one of said plurality of groups of lattice patterns comprise other inclined lattice patterns symmetrical with said inclined lattice patterns.

4. An interpolation encoder according to claim 1, characterized in that said inclined lattice patterns comprise line patterns.

5. An interpolation encoder according to claim 1, characterized in that said inclined lattice patterns comprise patterns of Archimedes'"'"' spirals.

6. An encoder for measuring a two-dimensional displacement which comprises a code plate having a plurality of blocks, each of said blocks having address data representing an address of said block and having interpolation patterns comprising periodic lattice patterns including lattice pattern information "1" and "0" alternately, a sensor array having a plurality of sensor elements continuously arranged in an array, and an arithmetic unit for processing data detected by said sensor array from said code plate, characterized in that;

said lattice patterns are formed by lattice patterns whose arrangement is inclined with respect to the arrangement of said sensor elements of said sensor array,

whereby the number of lattice patterns within a predetermined length of said code plate is slightly different from the number of said sensor elements of said sensor array within a length corresponding to said predetermined length so that a vernier relationship is established between the lattice patterns of said code plate and said sensor array, and

said arithmetic unit is provided with means for obtaining an intersected position of an output envelope of even-numbered elements and an output envelope of odd-numbered elements of said sensor array for obtaining an interpolated value within the width of the sensor element,

whereby the displacement of said code plate in the longitudinal direction of said sensor array and in the direction perpendicular thereto can be detected independently with high precision.

7. An encoder according to claim 6, characterized in that said code plate is moved in one normal direction of displacement to be measured, and said arithmetic unit has a means for cancelling errors in the direction perpendicular to the direction of said normal displacement to be measured.

8. An encoder according to one of claim 6 or 7, characterized in that said blocks of said code plate respectively have fine reading patterns comprising line patterns inclined with respect to said sensor array for indicating fine displacements within each of said blocks.

9. An encoder according to claim 8 characterized in that said fine reading patterns are different in thickness, number, or transmittance from one to another.

10. An encoder according to one of claims 6 and 7, characterized in that said fine reading patterns comprise Archimedes'"'"' spirals.

11. An encoder according to claim 10, characterized in that said interpolation patterns comprise at least one track having a plurality of Archimedes'"'"' spirals.

12. An encoder according to one of claims 6 and 7, characterized in that said interpolation patterns are inclined with respect to said sensor array and comprise at least one track having a plurality of parallel lines.

13. An encoder according to claim 12, characterized in that said track consists of two tracks, at least one of which is inclined to said sensor array and has a line patterns consisting of a plurality of parallel lines.

14. An encoder according to claim 12, characterized in that at least two said tracks are incorporated, and at least one of said tracks has line patterns symmetrical with said line patterns of the other of said tracks.

15. An encoder according to claim 6 or 7, characterized in that said address data comprise gray codes.

16. An encoder according to claim 6 or 7, characterized in that said blocks relatively has a reference track for designating a reading start bit of said sensor array.

17. An encoder according to claim 6 or 7, characterized in that said code plate comprises an optical code plate, said sensor array comprise a group of photoelectric converting elements, a projecting optical system is interposed between said code plate and said sensor array, and said interpolation patterns and/or said fine reading patterns are formed symmetrically with each other about a plane including an optical axis of said projecting optical systems.

18. An incremental encoder for measuring a two-dimensional displacement which comprises a code plate having interpolation patterns comprising periodic lattice patterns including lattice pattern information "1" and "0" alternately, a sensor array having a plurality of sensor elements continuously arranged in an array, and an arithmetic unit for processing data detected by said sensor array from said code plate, characterized in that;

said code plate has a reference pattern, fine reading patterns, and interpolation patterns,

the arrangements of said fine reading patterns and said interpolation patterns respectively are inclined with respect to an arrangement of said sensor elements of said sensor array,

said lattice patterns are formed by lattice patterns whose arrangement is inclined with respect to the arrangement of said sensor elements of said sensor array,

whereby the number of lattice predetermined length of said code plate is slightly different from the number of said sensor elements of said sensor array within a length corresponding to said predetermined length so that a vernier relationship is established between the lattice patterns of said code plate and said sensor array, and

said arithmetic unit is provided with means for obtaining an intersected position of an output envelope of even-numbered elements and an output envelope of odd-numbered elements of said sensor array for obtaining an interpolated value within the width of the sensor element,

so that displacement of said code plate in the longitudinal direction of said sensor array and in the direction perpendiculr thereto may be detected independently with high precision.

19. An incremetal encoder according to claim 18, characterized in that said code plate is moved in one normal direction of a displacement to be measured, and said arithmetic unit has a means for cancelling errors in the direction perpendicular to the direction of said normal displacement to be measured.

20. An encoder according to claim 18 or 19, characterized in that said fine reading patterns and said interpolation patterns comprise line patterns, and said interpolation patterns comprise at least two inclined lattice patterns which are symmetrically oriented with each other.

21. An encoder according to claim 18 or 19, characterized in that said reference pattern comprises line patterns parallel to said direction of displacement of said code plate.